Mortal
by amabethchase
Summary: Sizzy one-shot in which Simon turns mortal to save his life and be with Isabelle. Takes place during COHF.


Isabelle couldn't find Simon anywhere.

She couldn't find anyone, for that matter, but she knew Jace would keep Clary safe, and same for her brother and Magnus; she wasn't looking for someone to protect _her_. She wanted to protect him.

"SIMON," she shouted for the eighth time, picking her way through the rubble that had once been the first battlefield of the Mortal War. The demons and Shadowhunters had moved on, and she was supposed to be with them, but she was the only one who knew Simon was lost. Jace told her, just before he'd left, but he hadn't told Clary because she needed to focus completely on her runes. The runes that were winning the war.

"_Simon," _Isabelle cried, desperate now. He wasn't dead. He couldn't be. Not only was he a vampire, but he was hers now. And he was going to be hers for a long time and she didn't want that time to be cut short yet.

A mangled voice called, "Iz," and she was both startled and relieved to hear it was close by.

"Simon?" She called again, moving faster, now running up the huge hill Sebastian had sat perched on, watching smugly as his demon army attacked the Shadowhunters below.

"Iz," she heard again, when she reached the top, out of breath but newly exhilarated, and she rushed to clear away a mound of tree branches glued together with some kind of demonic substance.

Her hands burned and her muscles strained but she didn't care; Simon was here. He was speaking; he was alive.

Finally she cleared the last, heaviest branch and saw Simon, lying flat on his back, looking more battered than the time he'd died at their footsteps in the Institute, the night he'd tore out of his own grave to become a vampire. Bruises marred his skin, blood seeped through several spots on his shirt, his eyes were swollen and shut.

"_Simon," _she whispered, horrified, kneeling beside him. "Who did this to you?"

A small smile cracked his lips. "Vampires don't make the best demon-slayers, apparently."

"By the Angel." She surveyed his injuries, and they looked bad. His right leg was broken, along with his left wrist and possibly even his nose. His hair was muddy and matted with blood.

"You have to go," he said, eyes still shut. "Isabelle, you have to fight—"

"No," she said firmly, resting her head on his chest. "I'm not going anywhere."

"The war—"

"Is being fought by hundreds of Shadowhunters." She was glad he couldn't see her cry, though maybe he could hear it in her voice. Simon, the only boy she'd ever really, truly loved, was fading from her fast.

The coldness of his chest, the lack of a heartbeat, reminded her: "Why aren't you healing?"

"Sebastian," he said angrily. "He poisoned me."

"How?"

"Had a Larex demon inject me with it," Simon explained. "At least, that's what he told me it was. That it would injure Shadowhunters and kill Downworlders." Speaking seemed to take great effort from him.

_Larex demons. _She remembered those, from a textbook several years ago. They were rare, almost extinct, but of course Sebastian would summon them. Was Max not enough? Did he have to take everything she loved? Who was next, her _parabatai? _She and Clary had just performed the ceremony last week, but he'd know.

"There has to be a way . . ." Isabelle said, more for herself than Simon. There was no way, though. Simon was going to die. And she was going to have to watch him, because Sebastian knew she couldn't leave him here alone.

"It's okay, Iz." Simon's eyes opened slightly, and they shone as he smiled at her. "I'm glad I got to help you all. What would you have done without my sexy vampire mojo to pave the way to victory?"

Despite everything, she laughed.

"There is a way."  
Simon, startled, looked to Isabelle, but she was just as confused. She jolted upright, and saw a black-cloaked figure moving slowly towards them. She stopped about ten feet away.

"Who are you?" Izzy demanded, stretching to cover Simon's body protectively.

"I am an Iron Sister," she replied. "You may call me Theresa."

An Iron Sister. Isabelle remembered visiting them with Jocelyn; she remembered how creepy they were, but this one sounded normal. Kind, even.

"What were you saying?" Izzy asked, sitting upright again.

"There is a way to save him," Theresa said. "He can turn mortal."

"I can do that?" Simon said incredulously.

"If you so choose," she nodded.

"That doesn't make any sense," Isabelle countered.

"I have the power to turn him mortal," Theresa said. "If he does choose to do this, I will be able to heal his injuries. If not, there is no way that I can match the Larex poison."

"Do it!" Isabelle said immediately. "Come on, he's dying!"

"Wait," the Iron Sister said calmly. "Not everyone survives the transition from Downworlder back to human."

Isabelle's heart fell. She wanted Simon, but she didn't want to be the one who killed him.

Simon coughed. "It's okay, Iz," he said. "We have to risk it."

"But—"

"It's this, or I die from demon poison, correct?" Theresa nodded. Simon, struggling to open his swollen eyes, smiled up at Isabelle. "Don't worry. I didn't particularly enjoy being a vampire anyway."

Izzy smiled back, and she looked up at Theresa. "Please turn him mortal."

She nodded, and Isabelle got up and moved aside as the Iron Sister moved towards them. She still held Simon's hand, tightly, but Theresa gently moved her away.

Isabelle watched anxiously, and curiously—she'd never heard of any Iron Sister or Silent Brother who could do something like this—as Theresa knelt down beside Simon. Her fingers began to glow and sparkle, like Magnus's but dark purple.

Circling her hand over Simon's lifeless chest, she began chanting softly, Latin words Izzy didn't understand. She felt lightheaded; she hadn't realized she'd been holding her breath.

Simon began to cough, choking, and Isabelle winced. _By the Angel, let him live, _she prayed silently. _He's done nothing but help us. And so many people would be devastated—Clary, especially, and I know Jace would miss him too. And I . . ._

She had to look away. If Simon wasn't going to make it, she couldn't watch.

The coughing subsided, and Simon let out a yelp as Theresa presumably began healing his injuries, which meant . . .

"Simon!" Isabelle cried, running back and kneeling beside her boyfriend, watching his chest rise and fall like a human's. She could practically hear his heart resume beating, blood coursing through him, could see his skin gaining color again.

"Patience," the Iron Sister chastised. "This is a big transition for him. Give him a few minutes to speak."

She couldn't believe this. Not only was Simon not going to die, but he was going to be really _alive _again. They could be together. She, Isabelle Lightwood, was going to be in a relationship with a mundane. She couldn't wait to tell Clary. She decided to leave out the part where her best friend nearly died and had to be healed by a mysterious Iron Sister.

Suddenly Simon gasped, a huge intake of breath, and sat bolt upright as he exhaled. "Iz?" He asked, panicked, his hand flying to his chest, where he'd now feel a heartbeat.

"You're pretty strong for a mundie," she teased him, leaning in to kiss him. She didn't care that Theresa was watching; all that mattered was Simon.

He kissed her back, and she felt his hands tangle in her hair, which had at some point slipped out of its ponytail. His lips were warm again, soft, and she kissed him harder than she had in weeks. There was still a slight aftertaste of blood in his mouth, but his injuries were healed.

Isabelle pulled away, breathing, "Thank you," but the Iron Sister was gone. She sat for a moment, breathing hard, wondering why she'd left the Adamant Citadel and come to Idris, of all places. Wouldn't she want to steer clear of the war?

"Who was that?" Simon asked, still in shock.

"I don't know," Isabelle answered honestly.

"Izzy," Simon said, reaching to cup her face in his hands, "I love you."

She smiled. "I love you, too, but you know that."

"I thought 'hearts were breakable'," he said skeptically. "That you'd never give yours away."

"I didn't _give _it away," she corrected, "You kind of stole it. And you'd better not break it."

"Wasn't planning to," Simon said, and he pulled her back down on top of him, kissing her and making her forget about everything else: her new _parabatai, _Sebastian, the war. She knew they'd have to reenter the fighting, the real world, but for that moment all that mattered was the relief she'd felt, and vengeance against Sebastian. He hadn't taken everything from her. She'd won.

**Sorry it's kind of terrible; I just really like Sizzy and Tessa and I wanted to write a short fic about them all. At least I won't be adding any more chapters!**


End file.
